DEEP: MTBE Information

MTBE - Methyl Tertiary Butyl Ether

The federal Clean Air Act (CAA) requires that certain areas that exceed the National Ambient Air Quality Standards for ground level ozone, including Connecticut, use reformulated gasoline (RFG). The CAA specifies RFG must achieve a set of emission performance standards and, until May 2006 required the RFG to meet a minimum oxygen content (oxygenate). The RFG program was designed to reduce emissions of volatile organic compounds (VOCs) and nitrogen oxides, and toxics from motor vehicles. Oxygenates also reduce carbon monoxide emissions.

Methyl-Tertiary-Butyl Ether (MTBE) was the oxygenate chosen by fuel suppliers to meet the RFG oxygenate requirement in the Northeast. MTBE was readily available at a reasonable cost and blended easily with gasoline at the refinery. MTBE also has a collateral benefit of reducing toxic air pollutants, the majority of which are VOCs, beyond the minimum reductions specified by the CAA for RFG.

The use of MTBE increased significantly in the 1990s. As discussed above, it was added as a way of complying with the RFG requirements, and it was very effective in reducing the emissions of carbon monoxide and toxics. However, as air pollution emissions decreased, the incidence of MTBE contamination of groundwater increased significantly. Unfortunately, because of its concentration in gasoline products and its characteristics in groundwater, MTBE contaminated many more wells than would have otherwise been affected if it were not present in gasoline.

These groundwater contamination concerns led several states, including Connecticut, to enact restrictions on the use of MTBE in gasoline. On July 1, 2000, Public Act 00-175 (now codified at Section 22a-450a of the Connecticut General Statutes) was enacted, effectively banning the sale and use of MTBE as an additive in gasoline in Connecticut, and requiring that the Department of Environmental Protection (DEP) develop a plan to implement the ban in Connecticut. Subsequent amendments to the law changed the effective date of the ban of MTBE as a gasoline additive to on or after January 1, 2004. CGS Section 22a-450a also required DEP to seek a waiver from the US Environmental Protection Agency for the purpose of discontinuing the use of MTBE.

Because the federal oxygenate requirement for RFG remained in effect after the ban on MTBE, ethanol, the only viable oxygenate for Connecticut at that time replaced it. However, as of May 5, 2006, under the federal Energy Policy Act of 2005, the oxygenate requirement for RFG is no longer in effect.  The Energy Policy Act of 2005 also requires a large increase in ethanol production to be used as motor fuel.  Because fuel suppliers have existing infrastructure to blend ethanol in gasoline due to the previous RFG oxygen content requirement and due to the increasing use of ethanol under the Energy Policy Act of 2005, gasoline in Connecticut may continue to have ethanol in it.

Information on Phasing Out the Use of MTBE in Connecticut 

Documents Related to Connecticut's Request to EPA for a Waiver of the RFG Oxygen Content Requirement

Notice to EPA of Connecticut's Intent to Request Waiver of the Federal Reformulated Gasoline (RFG) Program's Requirement that Complying Fuels Contain a Minimum of 2 Percent Oxygen by Weight, April 2002 (PDF, 692K)

Connecticut's Formal Waiver Request Updated from the 2002 Submission, September 2004 (PDF, 20872K) 

Information for Suppliers/Retailers 

Ethanol 101 for the Retailer -  Independent Connecticut Petroleum Association (ICPA) Presentation

US Department of  Energy (DOE) Report on Preparations for Meeting New York and Connecticut MTBE Ban

Health, Environmental and Economic Impacts of Adding Ethanol to Gasoline in the Northeast States  
(Report by New England Interstate Water Pollution Control Commission (NEIWPCC) and Northeast States for Coordinated Air Use Management (NESCAUM)

Documents Related to California's Request to EPA for Waiver of the RFG Oxygen Content Requirement

Technical Support Document: Analysis of California’s Request for Waiver of the Reformulated Gasoline Oxygen Content Requirement for California Covered Areas (June 2001)

6/12/2001 - EPA Decision on California Waiver Request

Other Information on MTBE

Annual Reports on Use of MTBE as a Gasoline Additive

MTBE in Drinking Water - Department of Public Health Fact Sheet